The cellular and molecular investigation of Wnt/FZD signalling during spinal cord neurogenesis

Spinal cord development has been studied extensively and is a model for embryonic patterning and cell differentiation. These processes are governed by extracellular and intracellular signaling and require gene transcription. Wnt signaling has been shown to be involved in dorsal-ventral patterning of the spinal cord, where it affects cell proliferation and specification. Wnt ligands bind to Frizzled receptors and Lrp5/6 coreceptors and initiate canonical, β-catenin-dependent, Wnt signaling. To determine important FZD receptors in chick spinal cord we analysed FZD expression patterns using in situ hybridization. In situ cryosections showed that FZD expression patterns are dynamic and specific along the dorsal-ventral axis of the spinal cord. Previous work in Xenopus showed that FZD10 acts through canonical Wnt signaling. However, which Wnt ligands activate FZD10 during neurogenesis remains unclear. Here, we investigate FZD10 expression, regulation and function in the chick developing spinal cord using in situ hybridization, in ovo electroporation and immunohistochemistry. FZD10 is expressed in the dorsal neural tube and overlaps with expression of Wnt1, Wnt3a, markers of dorsal progenitors and of interneurons. To examine Wnt1 and Wnt3ainteractions with FZD10 in vivo, developing spinal cords were electroporated with Wnt1 and Wnt3a individually. Targeted mis-expression of Wnt1 up-regulated FZD10 expression whereas Wnt3a did not. This may suggest that FZD10 exclusively interacts with Wnt1 to mediate its function during spinal cord development. Furthermore, the role of FZD10 was studied in vivo in developing spinal cords. FZD10 regulated cell proliferation and differentiation, suggesting that it is required for Wnt1 signal transduction and for spinal cord development. Lrp6 is involved in central nervous system development including spinal cord. In this study, in vivo experiments revealed that Lrp6 complements Wnt1/FZD10 mediated activation of dorsal markers during spinal cord neurogenesis. This could explain how Wnt signalling regulates sensory neuron formation in the dorsal spinal cord.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2016

Author dc:creator

• Alrefaei, Abdulmajeed

Language dc:language

en